I really like the 65 gal. I've had multiple tanks though this one is the biggest I've set up, and this size has a very nice depth vs length (1/2 deep as long), the 18" front to back lets you put some 3 dimensional aspects into the rock work. The added height vs a 40 breeder is helpful too.
My next favorite tank size is a 4' 120gal, which also has 1/2 depth vs length (actually had one, but never got it set up
).
And in all actuality, this tank is already feeling small to me
, and will only get more so as corals grow in.